Quantitation of Copper Tripeptide in Cosmetics via Fabric Phase Sorptive Extraction Combined with Zwitterionic Hydrophilic Interaction Liquid Chromatography and UV Vis Detection The glycyl l histidyl l lysine Cu2+ tripeptide complex attenuates lung inflammation and fibrosis in silicosis by targeting peroxiredoxin 6 ScienceDirect 07 MARGOLINA c_04 LORD_c GHK Cu is a naturally occurring tripeptide in human plasma. Levels average 200 ng ml at age 20 and drop to 80 ng ml by age 60 (Pickart et al., 2020). That decline tracks with GHK Cu: The Regenerative Peptide for Skin, Hair, and Healing Pulse & Remedy